The energy consumed for heating and cooling a building, and therefore the cost of heating and cooling, is a function of the difference between inside and outside temperatures of the building. When the inside and outside temperatures are the same, no heat generally flows into or out of the building. Further, a larger difference between the inside and outside temperatures generally results in more heat flowing into or out of the building. Accordingly, heat flowing out of the building during the heating season (e.g., winter) and heat flowing into the building during the cooling season (e.g., summer) generally require purchased energy (e.g., natural gas, electricity, etc.) to offset the flow so that a desired interior temperature of the building may be maintained.
As can be seen, if one can somehow control the inside temperature of the building to be as close to the outside temperature as possible during times when the building is not in use (e.g., nights, weekends, holidays, etc. for a commercial building), the amount of heat transferring into or out of the building during these times may be minimized. If the amount of heat transfer is minimized, then the cost of heating and cooling the building may be reduced as well.
Conventional heating and cooling systems employ a thermostat in the building to maintain a relatively uniform temperature in the building all the time. But this approach may result in a situation where heat loss during a non-use period of the building is greater than if the maintained temperature in the building is adjusted somewhat. That is, in this conventional approach, the maintained temperature in the building is not adjusted to reflect the changing temperature outside of the building.
Use of a timed thermostat or a timing device connected to a regular thermostat is one approach to remedy such a situation. For example, if the occupation time for a building is 7 a.m. to 5 p.m., one may lower the building's desired temperature from 72 degrees to a setback temperature of 62 degrees (in Fahrenheit) for the period from 5 p.m. to 6 a.m., during which the building is not being used. This is often referred to as a setback. However, further complications may arise from such timed temperature control.
In this prior approach, the selection of the building's desired temperature and non-use period is arbitrary. In the example above, there is no definite indication that maintaining a desired temperature of 62 degrees from 5 p.m. to 6 a.m. would maximize energy savings. For instance, returning the building's temperature to 72 degrees at 6 a.m. may not have been the optimum time with respect to energy savings. If the temperature was mild outside, returning the space to 72 degrees could have been put off until closer to the occupation time for the space. Further, the setback temperature (i.e. 62 degrees) itself was arbitrary, and more energy savings would result if the setback could have been lower. If, however, the setback is too low and the setback period too long, then the heating equipment is not be able to return the space to 72 degrees by the occupation time. For example, if it is very cold, 1 hour (e.g. 6 a.m. to 7 a.m.) may not be enough time for the heating equipment to raise the temperature back to 72 degrees from 62 degrees by the occupation time for the space (i.e. 7 a.m.). Thus, this approach fails to maximize energy savings in that the setback time and period are arbitrarily chosen, and it may fail to maintain a desired temperature during the occupation times of the building.
Also, during a long period of non-use (e.g., periods that last for days or weeks), the prior approach does not allow adjustment of the building's desired temperature because it is controlled by a simple timer. For instance, if the inside temperature of the building is set to be lowered on weekends during which the building is normally not in use, the prior approach does not automatically adjust the inside temperature (e.g., returning to normal room temperature) for an event to be held in the building during a particular weekend.
In light of these deficiencies of the prior systems and methods, a solution is desired to effectively control energy usage of a building.